Molecularly imprinted polymers for removal of trimethylamine n-oxide

ABSTRACT

The present disclosure features a composition, including molecularly imprinted crosslinked polymers that have been imprinted with trimethylamine N-oxide. The molecularly imprinted crosslinked polymers have specific binding sites for trimethylamine N-oxide, and a trimethylamine N-oxide absorption capacity of at least 0.5 mg/g.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Patent Application No.62/828,340, filed Apr. 2, 2019, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

End stage renal disease (ESRD), or kidney failure, affects more than660,000 Americans. The majority of them (about 420,000) depend onhemodialysis three times per week and 3-5 hours each time to sustaintheir lives. The annual cost of hemodialysis in the U.S. is about 42billion dollars. Traditional hemodialysis requires ESRD patients to betethered to the dialysis machine about the size of a refrigerator, whichconfines patients' lives to dialysis facilities. In addition, theintermittent nature of hemodialysis is far from the physiologicalcondition where the blood is continuously filtered by the kidney.Portable or even wearable hemodialysis machines will liberate ESRDpatients and provide continuous dialysis comparable to physiologicalcondition. The major obstacle towards this goal is to reduce the weightand volume of the current dialysis machines. Specifically, the dialysateconsumption for a traditional dialysis is about 120 L at each session.Dialysate storage limits the potential of portable hemodialysismachines. Removing specific toxins from the dialysate and recyclingdialysate may ultimately overcome a major obstacle towards portablehemodialysis machines.

Thus, there is a need for a composition and method for selective andefficient removal of toxins, such as trimethylamine nitrogen oxide, froma dialysate. The present disclosure fulfils these needs and providesfurther advantages.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

In one aspect, the present disclosure features a composition, includinga crosslinked polymer derived from: a monomer including a(C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or a combinationthereof; and a crosslinker including a (C₁₋₆ alkyleneglycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate,N,N′-methylenebisacrylamide, or any combination thereof. The crosslinkedpolymer is a trimethylamine N-oxide molecularly imprinted polymer (TMAOMIP), has specific binding sites for trimethylamine N-oxide, and has atrimethylamine N-oxide absorption capacity of at least 0.5 mg/g.

In another aspect, the present disclosure features a method of removingtrimethylamine N-oxide from a hemodialysis dialysate, including passingthe hemodialysis dialysate including trimethylamine N-oxide through thecrosslinked polymer (i.e., the TMAO MIP) described herein, and absorbingthe trimethylamine N-oxide onto the crosslinked polymer to remove thetrimethylamine N-oxide from the hemodialysis dialysate.

In yet another aspect, the present disclosure features a method ofmaking a crosslinked polymer, including polymerizing a monomer includinga (C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or any combinationthereof; and a crosslinker including a (C₁₋₆ alkyleneglycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate,N,N′-methylenebisacrylamide, or any combination thereof, at amonomer:crosslinker ratio of from 1:9 to 14:1, in the presence oftrimethylamine N-oxide (a template) and a solvent, to provide thecrosslinked polymer (the trimethylamine N-oxide molecularly imprintedpolymer). The crosslinked polymer includes specific binding sites fortrimethylamine N-oxide and a trimethylamine N-oxide absorption capacityof at least 0.5 mg/g.

In yet a further aspect, the present disclosure features achromatography column or chromatography cartridge, including a pluralityof particles including a crosslinked polymer derived from a monomerincluding a (C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or anycombination thereof; and a crosslinker including a (C₁₋₆ alkyleneglycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate,N,N′-methylenebisacrylamide, or any combination thereof. The crosslinkedpolymer is a trimethylamine N-oxide molecularly imprinted polymer (TMAOMIP), has specific binding sites for trimethylamine N-oxide, and atrimethylamine N-oxide absorption capacity of at least 0.5 mg/g. Theparticles have an average diameter of from 300 nm to 2000 nm.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thesubject matter of the present disclosure will become more readilyappreciated as the same become better understood by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a schematic showing an exemplary synthesis of trimethylaminenitrogen oxide (TMAO) molecularly imprinted polymer, and showing thestructure of a TMAO template.

FIG. 2 is a schematic representation of an embodiment of a hemodialysissystem.

FIG. 3A is a micrograph showing an embodiment of a molecularly imprintedpolymer (MIP) particle aggregate having about 20 μm maximum crosssection.

FIG. 3B is a micrograph showing an embodiment of polymer microspheres ofabout 2 μm diameter.

FIG. 4 is a graph showing TMAO absorption capacity over a range of TMAOequilibrium concentrations for an embodiment of TMAO MIP of the presentdisclosure, having a MAA to EGDMA ratio of 8:1.

FIG. 5 a bar graph showing a static absorption test of TMAO byembodiments of MIPs of the present disclosure, having various molarratios of monomer methacrylic acid (MAA) to crosslinker (EGDMA).

FIG. 6 is an illustration of an example of a chromatography column ofthe present disclosure.

FIG. 7A is a graph showing TMAO absorption under flow conditions for anembodiment of a MIP of the present disclosure (monomer tocrosslinker=8:1).

FIG. 7B is a graph showing TMAO absorption under flow conditions for aC18 reference resin.

FIG. 8 is a bar graph showing competitive binding assay of TMAO vs. DMSOby embodiments of MIPs of the present disclosure (1T=1 mmol of TMAOtemplate addition during polymer synthesis, 7T=7 mmol of TMAO templateaddition during polymer synthesis).

DETAILED DESCRIPTION

Molecularly imprinted polymers (MIPs) are synthetic “antibody mimics”with high specificity, excellent stability, and low cost. In the presentdisclosure, MIPs are used for removal of trimethylamine nitrogen oxide(TMAO) in dialysate by targeted removal of key toxins with little effecton other components of the dialysate. In particular, the presentdisclosure demonstrates that MIPs imprinted with TMAO, a uremic toxin inthe plasma of subjects with compromised kidney function (e.g., end stagerenal disease ESRD patients), can remove TMAO efficiently andselectively from a dialysate.

Definitions

At various places in the present specification, substituents ofcompounds of the disclosure are disclosed in groups or in ranges. It isspecifically intended that the disclosure include each and everyindividual subcombination of the members of such groups and ranges. Forexample, the term “C₁₋₆ alkyl” is specifically intended to individuallydisclose methyl, ethyl, C₃ alkyl, C₄ alkyl, C₅ alkyl, and C₆ alkyl.

It is further appreciated that certain features of the disclosure, whichare, for clarity, described in the context of separate embodiments, canalso be provided in combination in a single embodiment.

Conversely, various features of the disclosure which are, for brevity,described in the context of a single embodiment, can also be providedseparately or in any suitable subcombination.

As used herein, “specific binding” or “binding specificity” or“specificity” in the context of binding by MIPs refers to a preferentialbinding to a given molecule or target for which the MIP is designed for(e.g., TMAO) compared to a comparative molecule having a similar sizeand dipole moment (e.g., DMSO), or compared to other toxins in ahemodialysis dialysate.

As used herein, the term “substituted” or “substitution” refers to thereplacing of a hydrogen atom with a substituent other than H. Forexample, an “N-substituted piperidin-4-yl” refers to replacement of theH atom from the NH of the piperidinyl with a non-hydrogen substituentsuch as, for example, alkyl.

As used herein, the term “alkyl” refers to a saturated hydrocarbon groupwhich is straight-chained (e.g., linear) or branched. Example alkylgroups include methyl (Me), ethyl (Et), propyl (e.g., n-propyl andisopropyl), butyl (e.g., n-butyl, isobutyl, t-butyl), pentyl (e.g.,n-pentyl, isopentyl, neopentyl), and the like. An alkyl group cancontain from 1 to about 30, from 1 to about 24, from 2 to about 24, from1 to about 20, from 2 to about 20, from 1 to about 10, from 1 to about8, from 1 to about 6, from 1 to about 4, or from 1 to about 3 carbonatoms.

As used herein, the term “alkylene” refers to a linking alkyl group.

As used herein, the term “random copolymer” is a copolymer having anuncontrolled mixture of two or more constitutional units. Thedistribution of the constitutional units throughout a polymer backbonecan be a statistical distribution, or approach a statisticaldistribution, of the constitutional units. In some embodiments, thedistribution of one or more of the constitutional units is favored.

As used herein, the term “constitutional unit” of a polymer refers to anatom or group of atoms in a polymer, comprising a part of the chaintogether with its pendant atoms or groups of atoms, if any. Theconstitutional unit can refer to a repeat unit. The constitutional unitcan also refer to an end group on a polymer chain. For example, theconstitutional unit of polyethylene glycol can be —CH₂CH₂O—corresponding to a repeat unit, or —CH₂CH₂OH corresponding to an endgroup.

As used herein, the term “repeat unit” corresponds to the smallestconstitutional unit, the repetition of which constitutes a regularmacromolecule (or oligomer molecule or block).

As used herein, the term “end group” refers to a constitutional unitwith only one attachment to a polymer chain, located at the end of apolymer. For example, the end group can be derived from a monomer unitat the end of the polymer, once the monomer unit has been polymerized.As another example, the end group can be a part of a chain transferagent or initiating agent that was used to synthesize the polymer.

As used herein, the term “terminus” of a polymer refers to aconstitutional unit of the polymer that is positioned at the end of apolymer backbone.

As used herein, the term “hydrodynamic diameter” refers to the apparentsize of particle assemblies hydrated in a solvent (e.g., water), asmeasured by dynamic light scattering.

As used herein, a “crosslinker” is molecule containing two or morereactive functional groups that are separated at various lengths. Thereactive functional groups covalently react with two or morefunctionalities on one or more polymer strands to covalently bond thefunctionalities together to form a crosslink.

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of various embodiments of theinvention. In this regard, no attempt is made to show structural detailsof the invention in more detail than is necessary for the fundamentalunderstanding of the invention, the description taken with the drawingsand/or examples making apparent to those skilled in the art how theseveral forms of the invention may be embodied in practice.

As used herein and unless otherwise indicated, the terms “a” and “an”are taken to mean “one”, “at least one” or “one or more”. Unlessotherwise required by context, singular terms used herein shall includepluralities and plural terms shall include the singular.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words ‘comprise’, ‘comprising’, and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to”. Words using the singular or pluralnumber also include the plural and singular number, respectively.Additionally, the words “herein,” “above,” and “below” and words ofsimilar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of theapplication.

The description of embodiments of the disclosure is not intended to beexhaustive or to limit the disclosure to the precise form disclosed.While the specific embodiments of, and examples for, the disclosure aredescribed herein for illustrative purposes, various equivalentmodifications are possible within the scope of the disclosure, as thoseskilled in the relevant art will recognize.

All of the references cited herein are incorporated by reference.Aspects of the disclosure can be modified, if necessary, to employ thesystems, functions, and concepts of the above references and applicationto provide yet further embodiments of the disclosure. These and otherchanges can be made to the disclosure in light of the detaileddescription.

Specific elements of any foregoing embodiments can be combined orsubstituted for elements in other embodiments. Moreover, the inclusionof specific elements in at least some of these embodiments may beoptional, wherein further embodiments may include one or moreembodiments that specifically exclude one or more of these specificelements. Furthermore, while advantages associated with certainembodiments of the disclosure have been described in the context ofthese embodiments, other embodiments may also exhibit such advantages,and not all embodiments need necessarily exhibit such advantages to fallwithin the scope of the disclosure.

Crosslinked Molecularly Imprinted Polymers

Referring to FIG. 1, the MIPs of the present disclosure can be made byfirst assembling monomers 102 and crosslinkers 104 in the presence of aTMAO template 106, the chemical structure of which is shown in FIG. 1.The monomers 102 and crosslinkers 104 can be polymerized to provide apolymer matrix 108 surrounding the TMAO template 106, and the TMAOtemplate 106 can then be removed (e.g., by washing with a solvent inwhich the TMAO is soluble but in which the resulting polymer isinsoluble) to provide the molecularly imprinted crosslinked polymer 110,which can be in the form of a powder 114 or processed into a powder 114.The powder 114 can be in the form of microspheres or nanosphere ofpolymer 110. The powder 114 can then be incorporated into a column or acartridge 116, which can be integrated into a hemodialysis circuit (notshown) to remove TMAO from a dialysate.

As an example, MIPs for TMAO can be synthesized starting from a reactionmixture including TMAO which serves as a template, monomers (e.g.,methacrylic acid), crosslinkers (e.g., ethylene glycol dimethacrylate),and one or more solvents. The reaction mixture can include a radicalpolymerization initiator, such as azobisisobutyronitrile (AIBN), andoptionally a porogen. The reaction mixture can be heated under inertatmosphere for a period of time to provide the MIP. For example, thereaction mixture can be heated at a temperature of about 60° C. (e.g.,from 30° C. to 100° C., from 45° C. to 100° C., from 60° C. to 90° C.,from 60° C. to 75° C., about 50° C., about 55° C., about 65° C., orabout 75° C.) for about 24 hours (e.g., about 20 hours, about 15 hours,about 12 hours, or about 6 hours) under N₂ or argon, to provide the MIP.In some embodiments, rather than heating the reaction mixture, thereaction mixture can be irradiated with ultraviolet light in thepresence of a photoinitiator to provide the MIP. The MIP can be formedin situ as a nanoparticle or microparticle during synthesis, and/or theMIP can be processed into a powder after synthesis. The MIP powder canbe evaluated for TMAO absorption, for example, using high performanceliquid chromatography (HPLC), in tandem with mass spectroscopy (MS).

In some embodiments, the present disclosure features a composition,including a MIP (also referred to herein as a crosslinked polymer, or acrosslinked MIP) derived from: a monomer such as (C₀₋₆alkyl)acrylicacid, di(C₁₋₆alkyl)acrylic acid, and/or a combination thereof; and acrosslinker such as (C₁₋₆ alkylene glycol)-di(C₁₋₆alkyl)acrylate,trimethylolpropane trimethacrylate, and/or N,N′-methylenebisacrylamide.The crosslinked MIP has been imprinted with trimethylamine N-oxide. Thecrosslinked MIP has specific binding sites for trimethylamine N-oxideand a trimethylamine N-oxide absorption capacity of at least 0.5 mgs/g.

In some embodiments, when the monomer is di(C₁₋₆alkyl) acrylic acid, thetwo C₁₋₆ alkyl groups can be the same or different, such that each C₁₋₆alkyl group is independently selected from C₁ alkyl, C₂ alkyl, C₃ alkyl,C₄ alkyl, C₅ alkyl, or C₆ alkyl.

In some embodiments, the monomer is methylacrylic acid, ethylacrylicacid, propylacrylic acid, butylacrylic acid, pentylacrylic acid,hexylacrylic acid, dimethylacrylic acid, diethylacrylic acid, and/ordipropyl acrylic acid. In some embodiments, the monomer is methylacrylicacid, ethylacrylic acid, propylacrylic acid, butylacrylic acid,pentylacrylic acid, hexylacrylic acid, dimethylacrylic acid, and/ordiethylacrylic acid. In some embodiments, the monomer is methylacrylicacid, ethylacrylic acid, and/or dimethylacrylic acid. In certainembodiments, the monomer is methylacrylic acid and/or dimethylacrylicacid. In some embodiments, the monomer is acrylic acid and/ormethacrylic acid. In certain embodiments, the monomer is methylacrylicacid.

In some embodiments, the crosslinker is (C₁₋₆ alkyleneglycol)-di(C₁₋₆alkyl)acrylate, or trimethylolpropane trimethacrylate. Insome embodiments, the crosslinker is ethylene glycol dimethacrylate,propylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate,1,3-butylene glycol dimethacrylate, or any combination thereof. In someembodiments, the crosslinker is ethylene glycol dimethacrylate.

In some embodiments, the MIP is in the form of a plurality of particles,the particles having an average diameter of from 300 nm to 2000 nm(e.g., from 300 nm to 1500 nm, from 300 nm to 1000 nm, or from 300 nm to800 nm), as determined by scanning electron microscopy.

In some embodiments, the MIP is derived from a monomer to crosslinkerratio of from 14:1 to 1:9 (e.g., 10:1 to 1:5; 10:1 to 1:1; 10:1 to 5:1;10:1; or 8:1). In some embodiments, the monomer is present at a molepercentage of at least 10% (e.g., at least 20%, at least 30%, at least40%, at least 50%, at least 60%, at least 70%, at least 80%, at least90%, at least 92%) and/or at most 95% (at most 94%, at most 92%, at most90%, at most 80%, at most 70%, at most 60%, at most 50%, at most 40%, atmost 30%, or at most 20%), relative to the total moles of thecrosslinker(s) and monomer(s). In certain embodiments, the monomer ispresent at a mole percentage of about 89% (e.g., about 90%, or about94%), relative to the total moles of the crosslinker(s) and monomer(s).

In some embodiments, the crosslinker is present at a mole percentage ofat least 5% (e.g., at least 6%, at least 8%, at least 10%, at least 20%,at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, atleast 80%) and/or at most 90% (e.g., at most 80%, at most 70%, at most60%, at most 50%, at most 40%, at most 30%, at most 20%, at most 10%, atmost 8%, or at most 6%), relative to the total moles of thecrosslinker(s) and monomer(s). In certain embodiments, the crosslinkeris present at a mole percentage of about 11% (e.g., about 10%, or about6%), relative to the total moles of the crosslinker(s) and monomer(s).

In some embodiments, the MIP has a trimethylamine N-oxide absorptioncapacity of 0.075 mg/g or more (e.g., 0.1 mg/g or more, 0.2 mg/g ormore, 0.3 mg/g or more, 0.4 mg/g or more, 0.5 mg/g or more, 0.6 mg/g ormore, 0.7 mg/g or more, 0.8 mg/g or more, or 0.9 mg/g or more) and/or1.05 mg/g or less (e.g., 0.9 mg/g or less, 0.8 mg/g or less, 0.7 mg/g orless, 0.6 mg/g or less, 0.5 mg/g or less, 0.4 mg/g or less, 0.3 mg/g orless, 0.2 mg/g or less, or 0.1 mg/g or less). In some embodiments, theMIP has a trimethylamine N-oxide absorption capacity of 0.5 mg/g ormore. In some embodiments, the MIP a trimethylamine N-oxide absorptioncapacity of about 1 mg/g (e.g., 1.05 mg/g). The absorption capacity canbe related to the ratio of the monomer to crosslinker in the MIP. Forexample, a crosslinked MIP having a monomer to crosslinker ratio of 8:1can have a TMAO absorption capacity of about 1.05 mg/g. As anotherexample, a crosslinked MIP having a monomer to crosslinker ratio of 8:1can have a TMAO absorption capacity of about 1.05 mg/g, when the monomeris MAA and the crosslinker is EGDMA. As another example, a crosslinkedMIP having a monomer to crosslinker ratio of 1:9 can have a TMAOabsorption capacity of about 0.075 mg/g, when the monomer is MAA and thecrosslinker is EGDMA.

The crosslinked MIP, or particles of the crosslinked MIP, selectively(e.g., more preferentially) and more efficiently bind to TMAO comparedto other molecules with similar steric and electronic properties (e.g.,dipole moment). For example, the crosslinked polymer, or a plurality ofparticles formed of the crosslinked polymer can have a lower dimethylsulfoxide (DMSO) absorption compared to TMAO absorption. In someembodiments, when exposed to a dialysate having equal amounts of TMAOand DMSO, a higher proportion of TMAO is absorbed by the MIP of thepresent disclosure compared to DMSO (e.g., 20 fold more, 10 fold more,or 5 fold more compared to DMSO). In some embodiments, the crosslinkedMIP, or particles of the crosslinked MIP has a dimethyl sulfoxideabsorption capacity of 0.11 mg/g (1.4 μmol/g) or less (e.g., 0.05 mg/gor less, or 0.01 mg/g or less).

The present disclosure also features a method of removing trimethylamineN-oxide from a hemodialysis dialysate, including passing thehemodialysis dialysate including trimethylamine N-oxide through thecrosslinked MIP described above, or through particles formed of thecrosslinked MIP described above, and absorbing the trimethylamineN-oxide onto the crosslinked MIP to remove the trimethylamine N-oxidefrom the hemodialysis dialysate. The crosslinked MIP can be regeneratedby removing the absorbed trimethylamine N-oxide. For example, toregenerate absorption capacity, the absorbed trimethylamine N-oxide canbe removed from the crosslinked polymer by washing the polymer with asolvent (e.g., deionized water, methanol, ethanol, a 0.01 M sulfuricacid aqueous solution, an aqueous buffer, and/or a dialysate) thatdissolves the trimethylamine N-oxide, but not the crosslinked polymer.

As discussed above, the crosslinked MIP can be in the form of aplurality of particles. The plurality of particles can be packed into achromatography column or a chromatography cartridge. In use, ahemodialysis dialysate can pass through the chromatography column orcartridge. In some embodiments, the hemodialysis dialysate is passedthrough the chromatography column or a chromatography cartridge at arate of 1 ml/minute or more (e.g., 10 ml/minute or more, 20 ml/minute ormore, 30 ml/minute or more, 40 ml/minute or more, 50 ml/minute or more,75 ml/minute or more, 100 ml/minute or more, 200 ml/minute or more, 300ml/minute or more) and/or 400 ml/minute or less (e.g., 300 ml/minute orless, 200 ml/minute or less, 100 ml/minute or less, 75 ml/minute orless, 50 ml/minute or less, 40 ml/minute or less, 30 ml/minute or less,20 ml/minute or less, or 10 ml/minute or less). In some embodiments, thehemodialysis dialysate is passed through the chromatography column or achromatography cartridge at a rate of about 40 ml/minute (e.g., about 60ml/minute, about 80 ml/minute, or about 100 ml/minute).

In some embodiments, the hemodialysis dialysate is passed through afilter to remove urea present in the hemodialysis dialysate prior to,concurrent with, or subsequent to passing the hemodialysis dialysatethrough the crosslinked MIP. For example, the hemodialysis dialysate canbe passed through a filter to remove urea present in the hemodialysisdialysate prior to passing the hemodialysis dialysate through thecrosslinked MIP.

In some embodiments, the hemodialysis dialysate can include one or moretoxins complexed with albumin. In some embodiments, the toxin(s)complexed with albumin can be separated from the albumin. The toxin(s)complexed with albumin carried by the dialysate can be wholly orpartially removed prior to, concurrent with, or subsequent to passingthe hemodialysis dialysate through the crosslinked MIP. As discussedabove, TMAO can be removed by the crosslinked MIP. In certainembodiments, the hemodialysis dialysate is first passed through a filterto remove urea, then through a filter to separate and/or removealbumin-bound toxins, and then through the crosslinked MIP to removeTMAO from the hemodialysis dialysate.

Methods of Making the Crosslinked Polymer

The present disclosure features a method of making a crosslinked MIP,including polymerizing a monomer such as a (C₀₋₆alkyl)acrylic acid,di(C₁₋₆alkyl)acrylic acid, or any combination thereof; and a crosslinkersuch as a (C₁₋₆ alkylene glycol)-di(C₁₋₆alkyl)acrylate,trimethylolpropane trimethacrylate, N,N′-methylenebisacrylamide, or anycombination thereof, at a monomer:crosslinker ratio as described above(e.g., from 1:9 to 14:1); in the presence of trimethylamine N-oxide,which can serve as a template; and solvent; to provide the crosslinkedMIP. The reaction mixture can include an optional porogen. The methodcan further include removing the trimethylamine N-oxide template fromthe crosslinked MIP, for example, by washing the crosslinked MIP with asolvent that dissolves the trimethylamine N-oxide but not thecrosslinked MIP. The resulting crosslinked MIP has specific bindingsites for trimethylamine N-oxide and has a trimethylamine N-oxideabsorption capacity of at least 0.5 mg/g.

In some embodiments, the method further includes grinding thecrosslinked MIP to form the plurality of particles of the crosslinkedpolymers. In certain embodiments, the crosslinked MIP is formed asparticles in situ in a reaction mixture including the monomer,crosslinker, trimethylamine N-oxide, and a solvent. When the crosslinkedMIP particles are formed in situ, the polymerization of the monomer andthe crosslinker can be conducted in a dilute reaction mixture, forexample, at a concentration of less than 180 mM (e.g., less than 200 mM,or less than 250 mM) to form a plurality of particles of the crosslinkedMIP.

In some embodiments, the solvent is any solvent or mixtures thereofwhere the monomer and crosslinker are soluble, but the crosslinked MIPis not soluble. The solvent can be a pore-forming solvent, such that acrosslinked MIP formed in the solvent has pores that are generated insitu during polymerization. For example, the solvent can beacetonitrile, methanol, water, a dialysate, or any combination thereof.

In some embodiments, the optional porogen can be a sacrificial solid,such as sodium chloride, polymethylmethacrylate microspheres, and/orpolymethylmethacrylate nanospheres, which can be removed from thecrosslinked MIP after the crosslinked MIP has been formed.

In some embodiments, the reaction mixture including the monomer,crosslinker, trimethylamine N-oxide, solvent, and the optional porogencan further include a radical initiator. For example, the radicalinitiator can include azobisisobutyronitrile, benzoyl peroxide, ammoniumpersulfate with N,N,N′N′-tetramethylethylenediamine (TEMED). In someembodiments, the reaction mixture can include a photoinitiator, and thereaction (i.e., polymerization) can be carried out under ultravioletillumination.

Assembly

The present disclosure also features a chromatography column orchromatography cartridge, including a plurality of particles including acrosslinked MIP described above. As discussed above, the crosslinked MIPcan be derived from, for example, a monomer including a(C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl) acrylic acid, or any combinationthereof; and a crosslinker comprising a (C₁₋₆ alkyleneglycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate,N,N′-methylenebisacrylamide, or any combination thereof. The crosslinkedMIP includes specific binding sites for trimethylamine N-oxide and atrimethylamine N-oxide absorption capacity of at least 0.5 mg/g. Theparticles including crosslinked MIP have an average diameter of from 300nm to 2000 nm.

The chromatography column can be a component of a hemodialysis system.The hemodialysis system can remove toxins from blood and recycle adialysate. Referring to FIG. 2, the hemodialysis system 200 can includea small pore filter 202; a large pore filter 204; and a chromatographycolumn or cartridge 206 including crosslinked MIP 116 of the presentdisclosure. In use, blood 208 containing toxins can pass through thesmall pore filter 202, and a dialysate 250 can remove urea. The blood208 then further passes through a large pore filter 204; and toxinscomplexed to albumin can be removed from the dialysate. The TMAO in thedialysate 250 is then removed by a chromatography column or cartridge206 including the crosslinked MIP 116 of the present disclosure.

In some embodiments, the hemodialysis system can be coupled with anon-transitory computer-readable medium having computer-executableinstructions stored thereon that, if executed by one or more processorsof a computing device, cause the computing device to instruct thehemodialysis system to perform one or more of the steps in a dialysissequence.

The following Examples describe molecularly imprinted polymers, theircharacterization, and evaluations of their TMAO absorption properties.

EXAMPLES Example 1. Evaluation of TMAO Absorption of MAA:EGDMA Vs.Acrylamide:EGDMA TMAO-Imprinted Polymers

General procedure: 300 mg polymers were put into a 20 mL scintillationvial. Then 10 mL 200 μM TMAO solution was poured into the vial. The vialwas sealed with a cover and put onto a shaker for an hour for TMAOabsorption. After that the remaining TMAO concentration (C_(remaining))in the solution was measured by HPLC/MS using 1 mL supernatant collectedfrom the vial. The removal efficiency was calculated as follows:

${{removal}\mspace{14mu} {efficiency}} = {\frac{{200\mu M} - C_{remaining}}{200\mu M} \times 100\%}$

TABLE 1 TMAO absorption for TMAO molecularly imprinted polymerssynthesized with methacrylic acid (MAA) and ethylene glycoldimethacrylate (EGDMA). MAA/EGDMA 1:9 1:5 1:1 2:1 3:1 4:1 8:1 11:1 14:1Ratio Removal 11.12 ± 19.78 ± 47.58 ± 68.39 ± 70.75 ± 76.07 ± 78.74 ±82.06 ± 83.56 ± efficiency(%) 13.4 8.01 6.42 5.61 2.11 0.58 3.99 3.233.51

MIPs have better performances at increasing MAA amounts incorporatedduring polymer synthesis. The increase in performance started to levelwhen MAA/EGDMA=8:1, but was best at MAA/EGDMA=14:1.

TABLE 2 TMAO absorption for TMAO molecularly imprinted polymerssynthesized with acrylamide (Aery) and ethylene glycol dimethacrylate(EGDMA): Acry/ EGDMA ratio 1:5 1:1 3:1 4:1 Removal −1.67 ± 19.7 −4.01 ±6.0 −1.53 ± 6.2 −31.2 ± 29.8 efficiency (%)

As shown in Table 2 above, negative efficiency means that the remainingTMAO concentration in the supernatant was higher than the original TMAOconcentration injected into vial in the beginning of the experiments.Without wishing to be bound by theory, it is believed that thisphenomenon was a result of the hydrophilicity of acrylamide. Polymerscontaining acrylamide could absorb a large quantity of water into itself(e.g., as much as 30 times of the polymer weight itself), which canresult in concentration of the TMAO solution. Thus, if polymers did notabsorb TMAO, the removal efficiency will be negative. Therefore, theseresults demonstrate that polymers made with acrylamide and EGDMA did notfunction to absorb TMAO.

Example 2—MAA:EGDMA TMAO-Imprinted Polymers with Additives

TMAO molecularly imprinted polymers were synthesized with methacrylicacid (MAA) and ethylene glycol dimethacrylate (EGDMA) at a 8:1 ratio,with small amounts of additives. The absorption capacity was evaluatedaccording to the general procedure in Example 1.

TABLE 3 TMAO absorption for acrylamide (Acry) and 2-hydroxyethylmethacrylate(HEMA) Additives, and Acry Acry Acry HEMA HEMA HEMA molarratio of 2% 4% 6% 2% 4% 6% additive to MAA Removal 81.64 ± 69.64 ± 64.98± 74.99 ± 71.29 ± 75.56 ± efficiency(%) 0.23 2.29 0.64 0.64 3.99 1.06

With additives such as acrylamide and HEMA, the MIPs behaveddifferently. For the acrylamide additive, the removal efficiencyincreased when 2% acrylamide was added, compared to samples withoutacrylamide. However, with more acrylamide addition, the MIPs absorptiondrastically decreased. HEMA additives slightly decreased the MIPs' TMAOabsorption ability overall, but the TMAO absorption ability did not seemto vary as a function of the amount of HEMA additive. In general, twomonomer additives did not appear to improve MIPs' performance.

Example 3—MAA:EGDMA TMAO-Imprinted Polymers with Varying TMAO TemplateAmounts

TMAO molecularly imprinted polymers were synthesized with methacrylicacid (MAA) and ethylene glycol dimethacrylate (EGDMA) at a 8:1 ratio,with varying amounts of TMAO template in the reaction mixture. Theabsorption capacity was evaluated according to the general procedure inExample 1.

TABLE 4 TMAO absorption for TMAO-molecularly imprinted polymerssynthesized from methacrylic acid (MAA) and ethylene glycoldimethacrylate (EGDMA) at 8:1 ratio with different amounts of TMAOtemplate during synthesis: 110 mg 330 mg 550 mg 770 mg TMAO amount (1mmol) (3 mmol) (5 mmol) (7 mmol) Removal 78.07 ± 0.67 81.34 ± 1.73 82.72± 1.36 81.43 ± 1.86 efficiency (%)

With more TMAO imprinted into the molecular imprinted polymer duringpolymer synthesis, the MIPs' TMAO absorption increased. The TMAOabsorption saturated at around 7 mmol of TMAO imprinted in about 5 gpolymer mass. Without wishing to be bound by theory, it is believed thatthe saturation could be related to the solubility limit of TMAO in thereaction solvent acetonitrile.

Example 4—Dimethylacrylic Acid:EGDMA TMAO-Imprinted Polymers

TMAO molecularly imprinted polymers were synthesized with3,3-dimethylacrylic acid (MAA) and ethylene glycol dimethacrylate(EGDMA). The absorption capacity was evaluated according to the generalprocedure in Example 1.

To investigate additional alkyl groups' influence on the MIPs'performance, MIPs were prepared using 3,3-dimethylacrylic acid and EGDMAwith 8:1 ratio.

TABLE 5 TMAO absorption for TMAO-molecularly imprinted polymerssynthesized from 3, 3-dimethylacrylic acid (MAA) and ethylene glycoldimethacrylate (EGDMA). Sample MAA MIPs 3, 3-dimethylacrylic acid MIPsRemoval 78.07 ± 0.67 9.88 ± 9.64 efficiency(%)

MIPs made using 3,3-dimethylacrylic acid and ethylene glycoldimethacrylate were not as effective as the corresponding MIPS usingmethacrylic acid and ethylene glycol dimethacrylate.

Example 5—Microscopy of MAA:EGDMA TMAO-Imprinted Polymer Particles

Representative synthesis for bulk TMAO-MIPs (e.g., MAA/EGDMA=8:1): adesired ratio of MAA and EGDMA (e.g., for an 8:1 ratio of MAA toEGDMA:64 mmol methacrylic acid and 8 mmol ethylene glycoldimethacrylate) was added into an Erlenmeyer flask with acetonitrile(e.g., 20 mL). a quantity of TMAO (e.g., 110 mg) was added into themixture. A radical initiator, azobisisobutyronitrile (AIBN), at 0.5%mass of the total monomers and crosslinkers (e.g., 35 mg) was added. Thereaction mixture was then shaken and purged with N₂ for 15 min. Theflask was put into a 60° C. water bath for a period of time sufficientto complete polymerization (e.g., 21 hours). A bulk molecularlyimprinted polymer was obtained. The bulk polymer can be ground toprovide microparticles. FIG. 3A is a scanning electron microscope imageof TMAO-MIP powder with a composition of 8:1 MAA:EGDMA, the powderobtained from a ground bulk polymer. The powder was in the form ofaggregates (˜20 μm) of microspheres of about 2 μm diameter.

Microspherical molecularly imprinted polymers: a desired ratio of MAAand EGDMA (e.g., 6.4 mmol methacrylic acid and 0.8 mmol ethylene glycoldimethacrylate (EGDMA)) was added into a 100 mL Erlenmeyer flask with alarge amount of acetonitrile (e.g., 40 mL for 6.4 mmol methacrylic acidand 0.8 mmol ethylene glycol dimethacrylate (EGDMA)). 11 mg TMAO wasadded into the mixture. A radical initiator, AIBN, at 0.5% mass of thetotal monomers and crosslinkers (e.g., 3.5 mg) was further added to thereaction mixture. The reaction mixture was then shaken and purged withN₂ for 15 min. The flask was put into a 60° C. water bath with constantstirring for a time sufficient to complete polymerization (e.g., 21hours). Microspheres of a molecularly imprinted polymer were obtained.FIG. 3B is a scanning electron microscope image of TMAO-MIP microsphereswith a composition of 8:1 MAA:EGDMA, generated in situ duringpolymerization in a dilute reaction mixture. The microspheres had adiameter of about 700 nm.

Example 6—Characterization of MAA:EGDMA TMAO-Imprinted Polymer Particles

Studies were carried out to investigate the binding behaviors over arange of TMAO concentrations and to determine the yield disassociationconstant for the binding between MIPs and TMAO.

10 mL of 10 μM, 25 μM, 50 μM, 100 μM, 200 μM, 500 μM and 1000 μM TMAOsolutions were added into 7 vials, each with 60 mg TMAO MIPs. Then thevials were put onto a shaker for one hour to establish equilibriumbetween the MIPs and TMAO solution. Supernatants from each vial werecollected and the remaining TMAO concentration in the supernatant wasmeasured with HPLC-MS. TMAO absorption capacity was calculated to be

${{absorption}\mspace{14mu} {capacity}} = \frac{\left( {C_{beginning} - C_{remaining}} \right)*V_{TMAO}*M_{TMAO}}{{polymer}\mspace{14mu} {mass}}$

where C_(beginning) is the original TMAO concentration added into thevial. C_(remaining) is the concentration of TMAO in the supernatant.M_(TMAO) is the molar mass of TMAO (75.11 g/mol) and V_(TMAO) is thevolume of TMAO solutions added into the via (10 mL). Polymer mass is themass of the MIPs put into the vial (60 mg).

FIG. 4 shows the absorption capacity of TMAO MIPs with MAA/EGDMA=8:1over a range of TMAO equilibrium concentration. The formula belowdescribes the isotherm curve, where the calculated disassociationconstant for binding between MIPs and TMAO is 250 μM and the maximumcapacity of TMAO MIPs is 5 mg/g.

${{absorption}\mspace{14mu} {capacity}} = \frac{{capacity}_{\max}*\lbrack{TMAO}\rbrack_{eq}}{\lbrack{TMAO}\rbrack_{eq} + K_{d}}$

In the formula, K_(d) is the disassociation constant for binding betweenMIPs and TMAO and capacity_(max) is the maximum TMAO absorption capacityfor MIPs. [TMAO]_(eq) is the concentration of TMAO at equilibrium.

The amount of water the polymer can absorb can be assessed bydetermining the swelling ratio, which is defined as the fractionalincrease in the weight of the polymer due to water absorption:

${{swelling}\mspace{14mu} {ratio}} = \frac{W_{s} - W_{d}}{W_{d}}$

where Ws is the polymer weight saturated with water and Wd is thepolymer dry weight. The swelling ratio of a 8:1 MAA:EGDMA TMAO-imprintedpolymer was 3.20.

Example 7—Flow and Static Absorption Evaluation of MAA:EGDMATMAO-Imprinted Polymer Particles

Evaluation of Molecularly Imprinted Polymer Capacity Under StaticConditions

Experimental procedures: 300 mg polymers were put into a 20 mLscintillation vial. Then 10 mL 200 μM TMAO solution was poured into thevial. The vial was sealed with cover and put onto a shaker for an hourto allow TMAO absorption approaching equilibrium. After that theremaining TMAO concentration C_(remaining) in the solution was measuredby HPLC/MS with 1 mL supernatant collected from the vial. The removalefficiency is calculated as follows:

${{removal}\mspace{14mu} {efficiency}} = {\frac{{200\mu M} - C_{remaining}}{200\mu M} \times 100\%}$

All experiments were done in triplicates.

FIG. 5 shows the results from static absorption tests of TMAO by MIPswith various molar ratios of monomer methacrylic acid (MAA) tocrosslinker (EGDMA).

Evaluation of Molecularly Imprinted Polymer Capacity Under FlowConditions

Experimental procedures: 0.5 g polymers were packed into a 60 mL syringebetween two frits as shown in FIG. 6. Briefly, one frit was positionedinto the bottom of the syringe. 0.5 g of polymer particles was addedinto the syringe. Another frit was placed on top of the polymer to sealthe polymer particles between the two frits. The upper frit was presseddown to tightly pack the polymer particles. Test solution can becontinuously flowed through the syringe column under flow conditions forevaluation of absorption capacity of a given MIP. To regenerate thecolumn, deionized water was continuously flowed through the syringecolumn until all TMAO absorbed onto the column was fully desorped. Theamount of water to use was found to be 300 mL water per 500 mg polymers.

To evaluate absorption capacity, TMAO solution of 200 μM continued toflow through the syringe. 1 mL supernatant coming out of the syringe wascollected at every 50 mL. The remaining TMAO concentration C_(remaining)in the supernatant was measured via HPLC/MS. The removal efficiency iscalculated as follows:

${{removal}\mspace{14mu} {efficiency}} = {\frac{{200\mu M} - C_{remaining}}{200\mu M} \times 100\%}$

The capacity was further calculated with the formula:

${capacity} = \frac{Area_{{under}\mspace{14mu} {the}\mspace{14mu} {curve}} \times M_{TMAO}}{{polymer}\mspace{14mu} {mass}}$

Where M_(TMAO) is the molecular weight of the TMAO (75.11 g/mol),polymer mass used in this experiment is 0.5 g.

FIGS. 7A and 7B are graphs showing TMAO absorption under flow conditionsfor MIPs (MAA:EGDMA=8:1) and a C18 reference resin. The TMAO solutionwas 200 μM, the experiment was conducted at a flow rate of 5 mL/min. Theabsorption capacity was calculated (the area under the curve) to be 1.05mg/g for MIP and <0.1 mg/g for the C18 reference resin.

Thus, TMAO removal efficiency of molecularly imprinted polymersincreases with higher monomer-to-crosslinker ratio. It is believed thatthe increase of capacity is likely due to the increase of the number ofavailable binding sites. The MIPs had much higher capacity than the C18reference. The absorption capacity of the a 8:1 monomer to crosslinkerMIP was measured to be 1.05 mg/g while the C18 reference had only lessthan 0.1 mg/g capacity. With such absorption capacity, only about 200 gof MIPs may be required to absorb all the TMAO cleared during onetypical dialysis (˜160 mg). The MIPs of the present disclosure were moreselective for TMAO over DMSO.

The TMAO absorption capacity was also evaluated for a range of flowrates. When the syringe for the column pack is 5 mL and polymer usage is0.5 g, the absorption capacities for different flow rates is indicatedin Table 6.

TABLE 6 Absorption capacity for MIPs of MAA/EGDMA = 8:1. 1 5 10 20 Flowrates mL/min mL/min mL/min mL/min Capacity 0.975 1.125 0.923 1.025(mg/g)

The TMAO absorption capacity under flow conditions was stable over arange of moderate flow rates.

Example 8—Competitive Test of TMAO and DMSO

Experimental procedures: 300 mg polymers were put into a 20 mLscintillation vial. Then 10 mL solution of 200 μM TMAO and 200 μMdimethyl sulfoxide (DMSO) was poured into the vial. The vial was sealedwith cover and put onto a shaker for an hour to allow equilibriumachieved. After that the remaining TMAO concentration C_(TMAO) and DMSOconcentration C_(DMSO) in the solution was measured by HPLC/MS with 1 mLsupernatant collected from the vial. The removal efficiency for eachcompound was calculated as follows:

${{TMAO}\mspace{14mu} {removal}\mspace{14mu} {efficiency}} = {\frac{{200\mu M} - C_{TMAO}}{200\mu M} \times 100\%}$${{DMSO}\mspace{14mu} {removal}\mspace{14mu} {efficiency}} = {\frac{{200\mu M} - C_{DMSO}}{200\mu M} \times 100\%}$

FIG. 8 is a bar graph showing the competitive binding of TMAO and DMSOby a MIP having an 8:1 ratio of MAA to EGDMA. Table 7 shows thequantitative values of removal efficiency of the polymer for TMAO andDMSO at 1 mmol of TMAO addition during synthesis, and at 7 mmol of TMAOaddition during synthesis (also shown graphically in FIG. 8).

TABLE 7 Removal efficiency of MAA:EGDMA for TMAO and DMSO Sample andTMAO 1T TMAO 1T TMAO 7T TMAO 7T target molecule DMSO TMAO DMSO TMAORemoval 11.80 59.58 3.80 85.14 efficiency(%)

MIPs for TMAO were successfully synthesized. MIPs show 2 orders ofmagnitude higher absorption capacity towards TMAO over commonnonspecific sorbents, for example C18. MIPs for TMAO also demonstrate abinding preference for TMAO over DMSO. MIPs developed have potential tobe used in portable hemodialysis machines for the specific removal ofTMAO toxin.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A composition, comprising: a crosslinked polymer derived from: a monomer comprising a (C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or any combination thereof; and a crosslinker comprising a (C₁₋₆ alkylene glycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate, N,N′-methylenebisacrylamide, or any combination thereof; wherein the crosslinked polymer comprises specific binding sites for trimethylamine N-oxide and a trimethylamine N-oxide absorption capacity of at least 0.5 mg/g.
 2. The composition of claim 1, wherein the crosslinked polymer is in the form of a plurality of particles, the particles having an average diameter of from 300 nm to 2000 nm.
 3. The composition of claim 1, wherein the crosslinked polymer is derived from a monomer to crosslinker ratio of from 14:1 to 1:9.
 4. The composition of claim 1, wherein the monomer is selected from acrylic acid, methacrylic acid, and any combination thereof.
 5. The composition of claim 1, wherein the monomer is methacrylic acid.
 6. The composition of claim 1, wherein the crosslinker is selected from ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate.
 7. The composition of claim 1, wherein the crosslinker is ethylene glycol dimethacrylate.
 8. The composition of claim 1, wherein the crosslinked polymer comprises a crosslinker mole percentage of at least 6%.
 9. The composition of claim 1, wherein the crosslinked polymer has a trimethylamine N-oxide absorption capacity of 0.075 mg/g or more and 1.05 mg/g or less.
 10. The composition of claim 1, wherein the plurality of particles has a dimethyl sulfoxide absorption capacity of 0.11 mg/g or less.
 11. A method of removing trimethylamine N-oxide from a hemodialysis dialysate, comprising: passing the hemodialysis dialysate comprising trimethylamine N-oxide through the crosslinked polymer of claim 1, and absorbing the trimethylamine N-oxide onto the crosslinked polymer to remove the trimethylamine N-oxide from the hemodialysis dialysate.
 12. The method of claim 11, further comprising washing the crosslinked polymer to remove the absorbed trimethylamine N-oxide from the crosslinked polymer.
 13. The method of claim 11, wherein the crosslinked polymer is in the form of a plurality of particles, the plurality of particles further contained in a chromatography column or a chromatography cartridge.
 14. The method of claim 13, wherein the hemodialysis dialysate is passed through the chromatography column or a chromatography cartridge at a rate of 1 ml/minute or more.
 15. The method of claim 11, further comprising passing the hemodialysis dialysate through a filter to remove urea present in the hemodialysis dialysate prior to, concurrent with, or subsequent to passing the hemodialysis dialysate through the crosslinked polymer.
 16. The method of claim 11, further comprising passing the hemodialysis dialysate through a filter to remove albumin-bound toxins present in the hemodialysis dialysate prior to, concurrent with, or subsequent to passing the hemodialysis dialysate through the crosslinked polymer.
 17. A method of making a crosslinked polymer, comprising: polymerizing a monomer comprising a (C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or a combination thereof; and a crosslinker comprising a (C₁₋₆ alkylene glycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate, N,N′-methylenebisacrylamide, or any combination thereof; at a monomer:crosslinker ratio of from 1:9 to 14:1, in the presence of trimethylamine N-oxide and a solvent, to provide the crosslinked polymer, wherein the crosslinked polymer comprises specific binding sites for trimethylamine N-oxide and a trimethylamine N-oxide absorption capacity of at least 0.5 mg/g.
 18. The method of claim 17, further comprising grinding the crosslinked polymer to form the plurality of particles of the crosslinked polymers.
 19. The method of claim 17, wherein polymerizing the monomer and the crosslinker is in solution at a concentration of less than 180 mM to form a plurality of particles of the crosslinked polymers.
 20. The method of claim 17, wherein the solvent is selected from acetonitrile, methanol, water, dialysate solution, or any combination thereof.
 21. The method of claim 17, further comprising a radical initiator.
 22. A chromatography column or chromatography cartridge, comprising a plurality of particles comprising a crosslinked polymer derived from: a monomer comprising a (C₀₋₆alkyl)acrylic acid, di(C₁₋₆alkyl)acrylic acid, or a combination thereof; and a crosslinker comprising a (C₁₋₆ alkylene glycol)-di(C₁₋₆alkyl)acrylate, trimethylolpropane trimethacrylate, N,N′-methylenebisacrylamide, or any combination thereof; wherein the crosslinked polymer comprises specific binding sites for trimethylamine N-oxide and a trimethylamine N-oxide absorption capacity of at least 0.5 mg/g, and wherein the particles having an average diameter of from 300 nm to 2000 nm. 